1. Field of the Invention
This invention relates to an umbilical member motion limiting device including a cable and/or a tube of an industrial robot. This invention also relates to a robot having the motion limiting device.
2. Description of the Related Art
When a robot performs a task, it is necessary to provide the robot with an umbilical member including a cable and/or a tube for transmitting power or a signal to an operating tool attached to the end of a wrist portion of the robot. When the umbilical member is arranged along the exterior of an arm and/or the wrist of the robot, surplus length of the umbilical member must be increased in order to provide a wider operating range of each axis at the wrist portion. However, surplus length causes the umbilical member to come into contact with external equipment, such as a workpiece or an operating tool, thus leading to damage of the umbilical member or external equipment. To prevent this, it is preferable to shorten the surplus length to thereby reduce an interference region, in which the umbilical member may contact or interfere with external equipment as much as possible. As a support provided around a wrist for reducing the interference region, Japanese Patent No. 3,944,208 discloses a guide member for reducing an interference region, which is used to attach the umbilical member to an exterior portion of the wrist between clamps respectively provided on a forearm and an end effector.
The guiding member for fixedly attaching the umbilical member to the wrist portion, as disclosed in Japanese Patent No. 3,944,208, requires increased surplus length of the umbilical member between the clamps in order to secure an operating range of each axis of the wrist portion, so as not to damage the umbilical member. As a result, the surplus length of the umbilical member loosens depending on the orientation of the wrist portion and thereby outwardly projects to the extent that the guide member cannot control the surplus length. Thus, the outward protrusion of the surplus length increases the interference region, and consequently, the umbilical member contacts or interferes with external equipment, and therefore tends to damage the umbilical member or external equipment.
Moreover, a certain orientation of the robot may make the position of the umbilical member unstable due to its own weight. For example, when an operating tool provided at the end of the wrist portion is directed downward, the umbilical member loosens excessively or extends downwardly around the external equipment due to its own weight. To stabilize the position of the umbilical member which has become unstable, i.e., to prevent the umbilical member from loosening or extending downward due to its own weight, it is possible to provide a cover that completely surrounds the umbilical member. However, there is a problem that with the addition of the cover to completely cover the umbilical member enlarges the interference region in which the cover interferes with the external equipment.